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| United States Patent |
5,086,262
|
|
Hariki
, et al.
|
February 4, 1992
|
Industrial robot system
Abstract
An industrial robot system comprising a plurality of robots for conducting
a work in cooperation with each other. A system clock is provided in the
system, and clocks are provided in the respective robots. These clocks are
counted up at the same cycle time, and are set for original points of the
respective robots, which are the waiting positions thereof, and the clock
values of the robots located in the respective positions during the drive
operation. During the drive of the system, the system clock is advanced by
adding a predetermined increment value thereto, and the respective robots
held under the enabling condition, start the operations by advancing the
robot clocks by adding the same increment value as that of the system
clock.
| Inventors:
|
Hariki; Kazuo (Toyama, JP);
Koizumi; Tatsuya (Toyama, JP);
Ishiguro; Kazuya (Toyama, JP);
Kanitani; Kiyoshi (Toyama, JP)
|
| Assignee:
|
Nachi-Fujikoshi Corp. (Toyama, JP)
|
| Appl. No.:
|
557071 |
| Filed:
|
July 25, 1990 |
Foreign Application Priority Data
| Current U.S. Class: |
318/568.1; 318/562; 318/568.11; 700/248; 700/249; 901/20; 901/21 |
| Intern'l Class: |
G05B 011/32 |
| Field of Search: |
318/41,562,564,568.11,568.12,568.2,601,616,618
364/573,513
901/3,9,12,20,21
|
References Cited
U.S. Patent Documents
| 3760251 | Sep., 1973 | Posl et al. | 318/601.
|
| 4617498 | Oct., 1986 | Ruppert | 318/41.
|
| 4629956 | Dec., 1986 | Nozawa et al. | 318/616.
|
Primary Examiner: Ip; Paul
Attorney, Agent or Firm: Spencer & Frank
Claims
What is claimed is:
1. A method for controlling an industrial robot system including a
plurality of robots arranged for conducting a job in cooperation with each
other, comprising the following steps of:
a) setting a system clock and a clock for each robot so that a
predetermined increment value is added to each clock in every constant
basic time period, each clock reaching a predetermined saturated value
just within a cycle time of the system, and then each clock again starting
to count from zero;
b) setting, for each of the robots, an original point clock value which is
a waiting position for starting an operation, and setting respective
positions of each robot during operation of that robot in accordance with
clock values of the clock associated with that robot; and
c) advancing the system clock by adding thereto the predetermined increment
value every constant basic time period during drive of the system, and
advancing the clock of each robot by adding thereto the predetermined
increment value whenever a robot corresponding to that clock is enabled.
2. The method according to claim 1, further comprising the step of:
(d) calculating a position which each robot reaches in every constant basic
time period of a recycle operation, by following the steps of:
1) obtaining a difference between a clock value of a present step and a
clock value of a next step for each robot;
2) obtaining a calculation number as to what multiple of the predetermined
increment value of the clock corresponds to the difference;
3) obtaining an increment value of position by dividing a difference
between a target position to be reached and a present position by the
calculation number;
4) obtaining a first complementary point by adding the increment value of
position to the present position; and
5) successively complementing the present position, calculating the present
position synchronously with the clock of the corresponding robot and
outputting the calculated position to the corresponding robot for the
operation by replacing the calculation number with "1" minus the
calibration number and repeatedly obtaining an n-th complementary point
from step 3) if "1" minus the calibration number is not zero.
3. The method according to claim 1, further comprising the steps of:
e) setting a safety operational range for each robot, within which, even
when a stop command is generated during a recycle operation of the system,
operation of the robot is continued, except for an emergency stop, from a
present step to an original point step when it is judged that any
operational interference and accidental release of a work may not occur;
and
f) conducting a predetermined safety stop of the robot which suffers from
an abnormality, transferring a stop signal to the other adjacent robots to
avoid interference between the robots, determining whether any other
robots are to stop or to continue operating until reaching their
respective original points by judging whether or not the other robots are
in the respective safety operational ranges, and preventing interference
between adjacent robots by transmitting the stop command to other robots
upstream and downstream from the robot with an abnormality.
4. The method according to claim 1, further comprising the step of:
g) setting availability/unavailability signals for controlling a supply of
power to each robot, and during teaching operation, supplying power only
to a robot to be taught.
5. The method according to claim 1, further comprising the steps of:
h) controlling information on a work, said controlling step including:
1) setting a work delivery association number representing which of the
robots receives the work from a subject robot;
2) setting a transfer mode number defining a method of handling the work to
an associated robot by releasing the work form the subject robot and
picking up the work of the associated robot from the subject robot; and
3) obtaining data of work conditions representing whether the work is
machined or not, whereby judging a condition of the work and a next
process concerning the work at any time; and
j) synchronizing the clock of each robot and the system clock by, in the
case where an associated robot holds the work during drive of the system,
enabling the robot when the system clock reaches the original clock value
of the robot, to start operating.
6. An industrial robot system comprising:
a plurality of robots each having at least one axis, arranged for
performing a job in cooperation with each other;
a teaching controller for moving the robots to conduct teaching thereof and
assigning a recordation of positions of the robots; and
a single robot controlling unit, said robot controlling unit comprising:
a) a system clock and a clock for each robot, a predetermined increment
value being added to each clock every constant basic time period, each
clock reaching a predetermined saturated value within a cycle time of the
system and then each clock starting to count again from zero;
b) program forming means for correspondingly recording values of the clock
of each robot in accordance with positions of the corresponding robot;
c) means for registering an original point of each robot corresponding to
the clock thereof, by setting the original point which corresponds to a
waiting position of the robot for starting operation and selecting any
step of a program as the original point;
d) means for advancing the system clock during drive of the system by
adding thereto a predetermined increment value every basic time period,
and advancing the clock of each robot by adding thereto the predetermined
increment value when the robot associated with that clock is enabled;
e) means for setting a safety operational range for each robot within which
operation of the robot is continued except for an emergency stop, in the
case where it is judged that, if continuing the operation up to the
original point of the robot after a present step, even when a stop command
is generated during a recycle operation of the system, any operational
interference and an accidental release of work may not occur;
f) abnormality transferring means for conducting a predetermined safety
stop of the robot which suffers from an abnormality, transferring a stop
signal to the other adjacent robots to avoid interference between the
robots, determining whether any other robots are to stop or to continue
operating until reaching the respective original points by judging whether
or not the other robots are in the respective safety operational ranges,
and preventing interference between adjacent robots by transmitting the
stop command to the other robots upstream and downstream from the robot
having the abnormality;
g) means for setting availability/unavailability signals for controlling a
supply of power to each robot, and during teaching operation, supplying
power only to a robot to be taught; and
h) controlling means for controlling information on the work, said
controlling means comprising:
1) means for obtaining a difference between a clock value of a present step
and a clock value of a next step;
2) means for obtaining a calculation number as to what multiple of the
predetermined increment of the clocks corresponds to the difference;
3) means for obtaining an increment value of position by dividing the
difference between a target position to be reached and a present position
by the calculation number;
4) means for obtaining a first complementary point by adding the increment
value of position to the present position; and
5) means for successively complementing the position, calculating the
position synchronous with the clock and outputting the calculated position
to the robot for operation by subtracting "1" from the calculation number
and repeatedly obtaining an n-th complementary point from 3) if the
subtracted number is not zero.
7. An apparatus according to claim 6, further comprising:
j) means for controlling information of the work, said controlling means
including:
1) means for setting a work delivery association number representing a
robot which receives the work from the subject robot;
2) means for setting a transfer mode number defining one of a method of
handing the work to the associated robot by releasing the work from the
subject robot and a method of picking up the work by the associated robot
from the subject robot; and
3) means for obtaining data of work conditions representing whether the
work is machined or not, whereby judging a condition of the work and a
next process concerning the work at an time; and
j) means for synchronizing the clock of each robot and the system clock by,
in the cane where the associated robot holds the work during drive of the
system, enabling the robot at the time when the system clock reaches the
original clock value of the robot to start operating.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an industrial robot system in which a
plurality of robots each having one or more axes are controlled by a
single control unit, and all the robots may be simultaneously operated in
synchronism with working machines additionally provided in the system.
A conventional industrial robot is composed of a single control unit, a
single machine body and a teaching controller for generating commands for
teaching. In the case where a work is machined or conveyed by using a
plurality of robots, of course, a plurality of control units are to be
used. Then, the robots must machine or convey the work in synchronism with
mutual interlock signals. For such synchronism, according to the mutual
interlock signals, there exists a method for starting of a subject
operation robot after it is detected that an associated robot is located
at a predetermined position and after it is confirmed that the subject
robot does not interfere with the associated robot even if the subject
robot is operated.
According to this method, the robot is operated after confirming that the
associated robot has stopped a the predetermined position or is not
located in the operational area where the subject robot is to be moved.
This results in a waste waiting period of time which is longer than
necessary for the operation itself. In addition, it is impossible to
transfer the work between the robots while the robots are being moved.
Namely, when the work is transferred to the associated robot or is
received from the associated robot, it is impossible to control the
relative moving speed of hands of these robots down to zero. It is
therefore necessary to give and take the work under the condition that the
respective robots are held in a stationary manner. For this reason, the
acceleration and deceleration of the robot bodies are carried out more
frequently than necessary, shortens mechanical service life of the robots
and leads to wasteful consumption of energy.
Thus, the conventional system composed of the plurality of robots could not
effectively be operated.
Also, a conventional robotic program is composed of steps for representing
reproduction order of the program, step data for representing physical
position of the steps, a time period for movement between the steps, and
some input/output signal processing for each step. Accordingly, a movement
period between the steps represents a designated time period for the
movement between two positions, and this time period differs from the
actual movement time. Although the total time for all of the designated
time periods of the respective steps should be the cycle time, each step
has an error and the error accumulates to generate a large error for the
cycle time as a whole. Furthermore, in the conventional positional control
method, commanded positional data are designated for a subsequent step
after confirming that the robot has reached the commanded position. For
this reason, a waiting time is added to the cycle time for every step, and
it is impossible to determine the cycle time unless the system is actually
in operation. Even if the plurality of robots are controlled by a single
control unit, it is impossible to make the cycle times of all the robots
the same in accordance with the foregoing positional control method.
Accordingly, although single wires are not actually connected to each
other, the synchronizing method for the robots within the system is
equivalent to the mutual interlock method.
SUMMARY OF THE INVENTION
An object of the invention is to provide an industrial robot system which
is capable of continuously operating respective robots and a working
machine without any waiting time.
Another object of the invention is to provide a control method for an
industrial robot system, according to which respective constituent
elements of the system can safely and smoothly operate without waiting
times.
Still another object of the invention is to provide a control method for an
industrial robot system, which is capable of operating a plurality of
robots in synchronism with each other only with a single control unit.
Still another object of the invention is to provide an industrial robotic
system which has a high efficiency without any waste time of the system by
the application of the above control method according to the invention.
The essential concept of the invention is that a system clock of an
industrial robot system and a clock of each robot are set to be counted up
at the same cycle time, and that the clock of each robot is advanced by
the same increment as that of the system clock during the driving
operation of the system. This implies that each instrument or unit of the
industrial robot system is controlled with substantially the same clock.
Therefore, by the method defined in appended claims according to one aspect
of the invention, a plurality of robots are operated at substantially the
same clock and are operated automatically in synchronism with each other
without effecting the mutual interlock. Accordingly, it is unnecessary to
take a mutual interlock between the plurality of robots unlike the prior
art, and there is no case where each robot is kept waiting in accordance
with the condition of an associated robot. By eliminating the waiting
condition, it is possible to reduce wasted time and energy to a minimum
possible level, which could not be attained according to the prior art.
Further, since a rapid acceleration/deceleration such as stop-start and
start-stop can be reduced, it is possible to prolong a mechanical service
life. Thus, more efficient operation of the system can be realized.
With the robot system according to another aspect of the invention, in view
of the problems inherent in the conventional robot system, a work may be
machined or conveyed without any mutual interlock and without any
necessity to stop the operation of respective units of the system.
Accordingly, it is possible to realize the robot system of high efficiency
from which the systems wasted time has been removed. In order to avoid or
eliminate the mutual interlock, according to the invention, a single
control unit is used to thereby operate a plurality of robots in
synchronism with each other, whereby it is possible to control the
position of an associated unit as well as the position of a subject unit
within the control unit. In addition, when transferring the work, an
external signal such as that from a limit switch or the like may be
dispensed with.
Also, according to the invention, formation of the program is modified so
as to control the plurality of robots at the same cycle time to thereby
completely eliminate the mutual interlock. Thus, an economical robot
system is realized.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a schematic view showing the overall structure of an industrial
robot system in accordance with an embodiment of one aspect of the
invention;
FIG. 2 is a block diagram showing the system shown in FIG. 1;
FIG. 3A is a flowchart of a process of a system control section shown in
FIG. 2;
FIG. 3B is a flowchart of a process of a system clock counting section
shown in FIG. 2;
FIG. 3C is a flowchart of a process of a clock supervising routine shown in
FIG. 3A;
FIG. 3D is a flowchart of a process of a stop checking routine shown in
FIG. 3A;
FIG. 3E is a flowchart of a process of an abnormality checking routine
shown in FIG. 3A;
FIG. 3F is a flowchart of a process of robot 1 controlling section shown in
FIG. 2;
FIG. 3G is a flowchart of a process of a robot 1 clock counting section
shown in FIG. 2;
FIG. 3H is a flowchart of a process o a robot 1 command position
calculating section shown in FIG. 2;
FIG. 4 is a schematic view for illustrating an operation of a robot
availability/unavailability selecting section shown in FIG. 2;
FIG. 5 is a diagram showing a relationship between a command position and a
calculation number according to the flowchart shown in FIG. 3H;
FIG. 6 is a schematic view for illustrating an operation of a robot 1
position data recording section shown in FIG. 2;
FIG. 7 is a timechart showing a clock cycle of the robot system shown in
FIG. 1 when the system is demanded to start and stop;
FIG. 8A is a schematic view showing an overall structure of an industrial
robot system in accordance with another embodiment of the invention;
FIG. 8B is a diagram showing operation loci of the respective robots shown
in FIG. 8A;
FIG. 9A is a flowchart of a process of a clock supervising routine for the
system shown in FIG. 8A; and
FIG. 9B is a flowchart of a process of a robot 1 controlling section in the
system shown in FIG. 8A.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the invention will now be described with reference to the
accompanying drawings.
FIG. 1 shows an industrial robot system in accordance with one embodiment
of the invention. The system is illustrated as an example for performing a
job for removing burrs of a work 3 by using two robots 1 and 2. In this
system, first robot 1 holds the work 3, and second robot 2 removes burrs
of work 3 by using a grinder 4. Robots 1 and 2 are respectively taught so
that clock signal values of clock signal generating devices correspond to
their positions and they perform the burr removal in cooperation with each
other in accordance with the increment of the clock signals.
FIG. 2 shows a structure of the control unit of the above-described robot
system. It should be noted that, although FIG. 2 additionally shows a
control portion for a third robot, this will be later used for explanation
of another example. FIGS. 3A through 3H are flowcharts respectively
showing the control flow of the control unit shown in FIG. 2. Each of
robots 1 and 2 may be a conventional robot provided with articulations of
one or more axes, and hence the detailed explanation of the structure and
operation of each robot will be omitted. The synchronous control of the
two robots will hereinafter be described.
Incidentally, herein, respective robots 1, 2 are set under the conditions
shown in Table 1 below. Robot 1 is referred to as an upstream unit i.e.,
master unit, and robot 2 is referred to as a downstream unit. Furthermore,
as is well known in the art, each clock signal is repeatedly generated at
regular intervals to be counted up. This counting is performed from zero
up to a certain number of clock signals, and is repeated after reaching
this certain number of clock signals. The increment value corresponds to
the number of clock signals increasing and increases at every regular time
period. The saturated value corresponds to the certain number of clock
signals at which the counting renews.
TABLE 1
__________________________________________________________________________
(Settings of Unit Operation)
ORIGINAL
POINT CLOCK VALUE UPSTREAM UNIT
DOWNSTREAM UNIT
UPSTREAM CLOCK
UNIT
__________________________________________________________________________
NOS.
ROBOT 500 (WORK SUPPLY
ROBOT 2 SYSTEM 1
1 UNIT) CLOCK
ROBOT 1000 ROBOT 1 -- ROBOT 1 2
2 CLOCK
__________________________________________________________________________
(saturated = 4000)
A section 2-A in FIG. 2 is composed of a system control section A-1, a
clock supervising section A-2, a system clock counting section A-3, and a
constant time interrupt generating section A-4.
Operation of system control section A-1 is carried out in accordance with
the flowchart shown in FIG. 3A. System control section A-1 drives or
starts stop checking routine 7, an abnormality checking routine 8 and a
clock supervising routine 9 after its own start. Then, the respective
routines 7, 8 and 9 repeat their processings whenever an interrupt is
generated from the constant time interrupt generating section A-4.
Subsequently, system control section A-1 checks in step a-1 whether or not
there is a start demand for the system. If the start is demanded, system
control section A-1 turns off a next cycle prohibition of all the units
(i.e., robots 1 and 2) in step 12; and further disables all the units
(operation stopping condition) in step 13. Subsequently, a system driving
flag (SYS) is set to "1" (driving ON) in step 14, thus completing the
process for the start demand. After that, until the flag SYS is .cent.0"
(driving OFF), the process is looped in block a-2. At the time when the
flag SYS is "0", the process is again in the start demand waiting mode in
step a-1.
Operation of the system clock counting section A-3 shown in FIG. 2 is
carried out in accordance with the flowchart show in in FIG. 3B. System
system clock counting section A-3 also repeats this process whenever an
interrupt is generated from the constant time interrupt generating section
A-4. Clock counting section A-3 checks whether the constant time interrupt
is generated or not (step 20), and whether the system is driven or not
(step b-1). If the system is in "driving ON", a system clock signal (CLK)
is increased by an increment value .DELTA.C in step 21, and is again
returned to zero in steps b-2 and b-3 when the signal has reached the
saturated value. The increment value .DELTA.C is determined by the
formula: .DELTA.C=A=ST/CYT where ST is the constant interrupt generation
cycle, CYT is a cycle time of the system and A is the saturation value of
each clock signal.
Subsequently, the foregoing clock supervising routine 9 (FIG. 3A) will be
explained. Clock supervising routine 9 is carried out in accordance with
the flowchart shown in FIG. 3C. The process is carried out whenever the
constant time interrupt is generated in step 22. A part c-1 in FIG. 3C
represents a processing part for enabling first robot 1 (in the operative
condition). First of all, it is checked whether or not the signal value of
the clock unit (system clock unit) upstream from robot 1 is identical to
the original point clock value of robot 1 in step 23. If not, the process
is ended. Namely, robot 1 is not enabled.
If the signal is identical to the original point clock value, robot 1 is
once disabled under no condition (step 24). Subsequently, robot 1 checks
whether or not the next cycle prohibition is turned off (step 25). If it
is turned off robot 1 is enabled (step 26). Robot 2 is also processed in
the same manner as in process section c-1 (step 27).
Thus, at the time when signals of the clock units upstream from the
respective robots coincide with the original point clock values of the
robot units, the respective robots may be enabled and the robots from the
upstream side to the downstream side may be synchronized with each other.
Subsequently, clock supervising routine 9 checks, in the process part c-2
of FIG. 3C, whether or not the signal of the clock unit of robot 1 is
identical to the original point clock value of robot 1 (step 28) and sets
the original point flag which indicates whether robot 1 is at the original
point or not (steps 29 and 30). The process similar to the process part
c-2 of FIG. 3C is effected on second robot 2 (step 31). The above
described routine clock supervising routine 9.
Subsequently, stop checking routine 7 shown in FIG. 3A will be explained.
Stop check routine 7 is carried out in accordance with the flowchart shown
in FIG. 3D. The process is performed whenever the constant time interrupt
is generated (step 32). Stop checking routine 7 checks the
presence/absence of the system stop demand first of all (step 33). If
there is the demand, the next cycle prohibition of the most upstream unit
(corresponding to robot 1 of the present system) is turned on (step 34).
Subsequently, in a process part d-1 of FIG. 3D, if robot 1 is disabled,
the next cycle prohibition is turned on for the unit downstream of robot 1
as the process for transmitting the stop of robot 1 to the unit downstream
from robot 1. In the system, if robot 1 is disabled and the next cycle
prohibition of robot 1 is turned on, the next cycle prohibition of the
unit downstream from robot 1 is turned on. Subsequently, the process
similar to the process part d-1 is applied to robot 2 (step 41).
Subsequently, stop checking routine 7 checks whether or not all the units
are disabled (steps 42 and 43). If disabled, the drive flag (SYS) is set
to "0" (driving OFF), thus terminating the process (step 44). This is
checking routine 7.
Abnormality checking routine 8 shown in FIG. 3A will be now explained.
Abnormality checking routine 8 is carried out in accordance with the
flowchart shown in FIG. 3E. The process is performed whenever the constant
time interrupt is generated (step 46). A part e-1 of FIG. 3E represents
the abnormality processing part of robot 1. First of all, the
absence/presence of the abnormality of robot 1 is checked. If there is the
abnormality, robot 1 is disabled (the operation is prohibited and the
robot is stopped as it is) (step 47). Subsequently, if there is the
upstream unit, it is checked whether or not upstream robot is kept in a
safety operational range (step 48). If the unit is out of the safety
operational range, the upstream unit is disabled and stopped. The safety
operational range referred to above means a range of positions of each
unit, in which if the upstream or downstream unit is stopped due to the
abnormality, and even if the robot continues the operation, there is no
fear that the robot would interfere with the upstream or downstream
stopped unit. The safety operational range is taught in advance within the
range of the corresponding clock signal values. For this reason, even if
the stop command due to the abnormality of the upstream or downstream unit
is effected, if the clock signal of the robot is in the range of the
safety operational range, the robot continues its operation, so that the
present operational cycle may be continued up to the original point. If
the clock signal is out of the safety range, the robot is stopped as it
is. Thus, since each unit continues its operation and stops at the
original point thereof, in as far as there is no risk of interference, it
is possible to avoid the unnecessary stop on the spot and to obviate the
job for returning the unit to the original point due to the midway stop.
According to the above described means, each unit is judged whether it is
to stop on the spot or continue operating.
Subsequently, abnormality checking routine 8 checks whether or not there is
any further upstream unit (step 49). If there is an upstream unit, the
process is returned back to step 48, and the same process is carried out
again. If there is no upstream unit, the next cycle prohibition is turned
on for all the upstream units (step 50). Thus, if the abnormality occurs
in robot 1, the abnormality is transmitted to the units upstream from
robot 1, one after another so that each unit is stopped on the spot or is
disabled and stopped at its original point by the next cycle prohibition.
Subsequently, abnormality checking routine 8 checks whether or nor there is
any unit downstream from robot 1. If there is a downstream unit, the
routine 8 checks whether or not the downstream unit is in its safety
operational range (step 51). If the unit is out of the safety operational
range, the downstream unit is disabled to be stopped at its present
position. Furthermore, the routine 8 checks whether or not there is any
further downstream unit (step 52). If any, the same process is carried out
in step 51. If the unit is in its safety operational range in step 51, the
next cycle prohibition of the downstream unit is turned on, thus
terminating the process. With such a routine, if the abnormality occurs in
robot 1, the abnormality is transmitted to the further downstream unit. If
each unit is out of its safety operational range, the unit is stopped at
its present site. If not, the operation thereof is continued up to its
original point with the next cycle prohibition turned on. Since the next
cycle prohibition is transmitted to the further downstream units by the
process part d-1 of the stop checking routine, the downstream units are
stopped one after another at the respective original points.
The above described is the abnormality processing on robot 1. Processing
part e-2 is applied to robot 2. This is the same as processing part e-1
but the abnormality checking routine.
The block 2-B of robot 1 shown in FIG. 2 will be explained. The block 2-B
of robot 1 is composed of a robot 1 control section B-1, a robot 1
operational condition registering section B-2, a robot 1 clock counting
section B-3, a robot 1 availability/unavailability selecting section B-4,
a robot 1 command position calculating section B-5, a robot 1 position
date recording section B-6, and a robot 1 servo amplifying section B-7.
The process of each section will be explained.
First of all, the process of robot 1 controlling section B-1 is carried out
in accordance with the flowchart shown in FIGS. 3F. In this section, it is
checked whether or not robot 1 is enabled (step 54). When robot 1 is
enabled, the following steps are effected. If robot 1 is enabled, the
command position of robot 1 is calculated in accordance with the present
value of the clock signal of robot 1 (step 55). The command position
signal is outputted to servo amplifying section B-7 of robot 1 (step 56).
Robot 1 controlling section B-1 has been described as to its operational
routine.
Subsequently, the operational condition registering section B-2 will be
explained. In this section, a variety of conditions such as the clock
value of the original point of robot 1 and conditions needed for the
operation of the upstream and downstream units as listed in Table 1 are
registered by the operation of teaching controller 6.
Subsequently, operation of the robot 1 clock counting section B-3 will be
described. The process of the robot 1 clock counting section is carried
out in accordance with the flowchart shown in FIG. 3G. It is checked (step
58) whether robot 1 is enabled or not whenever the constant time interrupt
is generated (step 57). Only when robot 1 is enabled, a value of a system
clock signal (CLK) is set to the robot 1 clock unit (CLK1) without any
modification. A similar process is performed in each of the other units.
When all the units are enabled to be operative, the clock units of all the
units have the same value as that of the system clock signal. In this
case, all the units are controlled in accordance with the same clock
signal.
Operation of robot 1 availability/unavailability selecting section B-4 will
be explained with reference to FIG. 4. In robot 1
availability/unavailability selecting section B-4, the availability
(operative) or the unavailability (inoperative) of robot 1 for the start
of the operation is selected by maneuvering teaching controller 6 (See
FIG. 2).
By selection of the availability, a contact for the robot selected in FIG.
4 is closed, so that power is supplied from servo amplifier units. In the
case of unavailability, since the contact is opened, power will not be
supplied. Thus, power is supplied to the robot which has been selected as
the available one, so that the robot is in a condition capable of
operating or being manually manipulated. On the other hand, if the robot
which is selected is the unavailable one, no power is supplied thereto.
Accordingly, there is no fear that an accident would occur due to any
unexpected or accidental operation of the robot during the operator's
maneuver for teaching. Also, since unnecessary power is not supplied to
the robot, it is possible to effectively save energy.
The operation of robot 1 command position calculating section B-5 will be
explained. In robot 1 command position calculating section B-5, the
command position is calculated in accordance with the flowchart of the
command value calculating routine shown in FIG. 3H. In this section, the
command position corresponding to the present clock value is calculated in
accordance with a present value of the clock signal, a clock value of the
present step, a position of the robot, a clock value of the next step, and
a robot position of the next step. The calculation method will be
explained assuming the following parameters:
clock signal increment interval: to t (seconds) . . . identical to the
constant time interrupt generating cycle
clock signal increment value: .DELTA.C (/unit time or /t seconds)
clock value of the present step S: Cs
position of the present step S: Ps
clock value of the next step S+1: Cs+1
position of the next step S+1: Ps+1
Also, assuming that the processing time period per one loop of controlling
section operational routine B-1 of robot 1 shown in FIG. 3F is within CT
seconds at maximum, the definition is made so that the command position
calculation may be performed at one time/CT seconds. However, there is a
relationship of t.ltoreq.CT. The following description will be made on the
assumption that there is the relationship of t=CT holds, that is, that the
clock signal increment interval is equal to the command value calculation
interval.
The increment number CNT1 of the clock signal during movement from the
present position to the point P.sub.s+1 is given by the following
expression:
##EQU1##
where CLK1 is the value of the clock signal of robot 1.
The clock signal increment number CNT2 within the command value calculation
interval is as follows:
##EQU2##
Therefore, the command value counting number CNT during movement from the
present position to the point P.sub.s+1 is as follows:
##EQU3##
The m-th time command value calculation formula during movement from the
present position to the point P.sub.s+1 is as follows:
##EQU4##
where n=CNT-m: m=0, 1, 2, . . . , CNT.
In the 0-th calculation of the command value, the calculation is performed
under the condition of n=CNT, and in the first calculation, the
calculation is performed based upon the value obtained by subtracting "1"
from n, i.e., CNT-1. Thereafter, Pn obtained by subtracting "1" from n
determining a new Pn and outputting Pn repeatedly as the command value,
and the command value reaches P.sub.s+1 under the condition of n=0. The
clock value Cs of the step S+1 and CLK 1 must be identical with each other
at n=0. This is the correct synchronized condition between the clock
signal and the position. If the value of CLK 1 is advanced beyond Cs+1,
the calculation number CNT is decreased to revert the synchronism. In the
flowchart shown in FIG. 3H, when the process is started, after the
above-described data have been read out, n=CNT is set in step 67, and the
command value Pn is calculated and outputted in step 68. Subsequently, n
is subtracted by "-1" in step 69, and it is judged whether or not n=0 in
step 70. Unless n=0, the process is continued as it is, whereas in the
case of n=0, in the step 71, step S+1 is regarded as present step S in
order to continue the process. FIG. 5 is a graph illustrating the
relationship between the above-described command position and the
calculation number.
Subsequently, the operation of robot 1 position data recording section B-6
will be explained. In this section, positional data of each axis of robot
1 and clock signals corresponding thereto are recorded by maneuvering of
teaching controller 6 as shown in FIG. 6. An a-part of FIG. 6 records "0"
or "1". The step recorded as "1" means the original point step, and the
clock value and the axis data of this step are dealt with as the original
point clock value and the original position, respectively. These data are
read out whenever the command position calculation is effected in robot 1
command position calculating section B-5.
Subsequently, operation of robot 1 servo amplifier section B-7 will be
described. In this section, the command position data calculated in robot
1 command position calculating section B-5 are received and the servo
amplifier is driven in accordance with the data, in order to operate the
respective motors of robot 1. The respective process contents of robot 1
block 2-B is described above. The same process is also applied to robot 2.
Subsequently, referring now to FIG. 7, operation, during the start demand
and stop demand, of robot system according to the previously described
respective sections will now be explained. Herein, it is assumed that the
operational conditions shown in Table 1 are set and first and second
robots 1 and 2 are located at their respective original points. If there
is a start demand at t=0, first of all, the system clock starts counting.
When the system clock which is an upstream clock of robot 1 becomes
identical to a clock value of the original point of robot 1, robot 1 is
enabled (at 72 in FIG. 7) and clock of robot 1 starts counting.
Thereafter, when the clock of robot 1 (which is an upstream clock of robot
2) become identical to the original point clock value of robot 2, robot 2
is enabled (at 73 in FIG. 7) and the clock of robot 2 starts counting.
Thereafter, when the stop demand is inputted at the clock value of, for
example, 3500 (at 74 in FIG. 7), robot 1 is placed under the next cycle
prohibition mode. At the time that the clock of robot 1 becomes identical
to the next original point clock value of robot 1, robot 1 is disabled (at
75 in FIG. 7). Thus, robot 2 is also subjected to the next cycle
prohibition. Then, at the time that the clock of robot 2 becomes identical
to the next original point clock value of robot 2, robot 2 is disabled (at
76 in FIG. 7) so as to be in the driving OFF mode at 77 in FIG. 7. Thus,
the two robots are enabled by transmission of the clock from the upstream
side of the system to the downstream side thereof. Also, robots are
operated, even though respective clocks are individual clocks, by
substantially the same clock. Thus, even during the burr removing job, the
two robots are operated in synchronism with each other to perform an exact
job.
Referring to FIG. 8A, there is shown an industrial robot system in
accordance with another embodiment of the invention. This system is
composed of three robots 101, 102 and 103, and a work 105 supplied from a
conveyor 100 is transferred through these robots in a direction 104 up to
a downstream conveyor 106.
More specifically, in the system according to this embodiment, work 105
supplied from conveyor 100 is received by first robot 101 and transferred
therefrom to second robot 102. Subsequently, work 105 is delivered from
second robot 102 to third robot 103 and further from third robot 103 to
conveyor 106. Robots 101, 102, 103 are respectively taught so that their
positions correspond to clock signals of their respective clocks (not
shown), and they operate to hand, receive and transfer work 105 in
accordance with increments of respective clock signals. Also in this
system, upstream conveyor 100 generates a drive signal (enabling signal)
during operation and a work existence signal upon sending work 105,
respectively. The respective robots are set, setting the first robot as a
master unit, in the operational conditions shown in Table 2. The
constitution and operation for control of this system are substantially
the same as those of the foregoing embodiment. In particular the control
of this embodiment is the same, except for the addition of the third
robot. FIG. 2 shows the control block for the third robot. Also, the
control process therefor is substantially the same as that shown in FIGS.
3A to 3H. Distinctions between the embodiments will now be explained.
TABLE 2
__________________________________________________________________________
SUCTION
SUCTION
MACHIN- UP- WORK
ORIGINAL ON OFF ING UP- DOWN- STREAM
TRAN-
CLOCK SWITCH
CLOCK CLOCK STREAM
STREAM CLOCK SFER UNIT
VALUE VALUE VALUE VALUE UNITS UNITS UNITS METHOD
NOS.
__________________________________________________________________________
ROBOT 1
1800 2000 600 *3300 CON- ROBOT 2 SYSTEM
1 1
VEYER CLOCK
ROBOT 2
2000 3500 1300 *400 ROBOT 1
ROBOT 3 ROBOT 1
1 2
CLOCK
ROBOT 3
700 800 3000 *1900 ROBOT 2
*CONVEYER
ROBOT 2
0 3
CLOCK
UNIT
__________________________________________________________________________
(saturation value = 4000)
Note 1: Mark * represents a unit imaginarily set.
Note 2: The number written in the column of the work transfer method
represents the operation as follows.
"0" represents transferring the work to an associated unit under no
condition;
"1" represents transferring and receiving the work in synchronism with th
associated unit; and
"2" indicates that the work is picked up by the associated unit under no
condition.
FIG. 9A shows a clock supervising routine 109 of this system. This
corresponds to routine 9 shown in FIG. 3A. Clock supervising routine 109
is carried out in accordance with a flowchart shown in FIG. 9A and
conducts a process every time the constant time interrupt is generated. A
section 134 in FIG. 9A is a processing section for enabling robot 101.
First of all, it is checked whether or not the signal value of a clock
unit (system clock unit) upstream from robot 101 is identical to the
original point clock value of robot 101 in step 133. If not, the process
is completed. Namely, robot 101 is not enabled. On the other hand, if the
signal is identical to the original point clock value, robot 101 is once
disabled under no condition (in step 137). Subsequently, it is checked
whether or not the next cycle prohibition of robot 1 is turned off (in
step 39). If it is turned on, robot 101 is not operative and the process
is terminated. Thus, it is possible to disable robot 101 at its original
point when robot 1 is under the next cycle prohibition. Furthermore, robot
101 is checked as to whether it is disabled or not. If disabled, robot 101
is enabled (step 153) under the condition of processing part 140 that the
upstream unit has the machined work and is enabled. Incidentally, although
robot 101 is the most upstream unit in this system, work supply unit,
i.e., conveyor 106 is regarded as the upstream unit of robot 101. Process
block 134 shown in FIG. 9A is similarly applied to second robot 102 and
third robot 103 (steps 154, 155). Thus, it is possible to enable the units
in accordance with the existence/absence of the upstream work at the time
when the signal of the clock unit upstream of each unit is identical to
the original point clock value of the unit itself. This results in
synchronizing the respective units with each other from the upstream side
of the system to the downstream side thereof. Subsequently, the process of
block c-8 is carried out. This is similar to block c-2 of FIG. 3C. The
process of block c-8 is applied similarly to robots 102 and 103 (steps
159, 160).
Subsequently, referring now to FIG. 9B, the operational routine of robot
101 will be explained. This corresponds to the process of FIG. 3F. In this
routine, it is first checked whether robot 101 is enabled or not (step
161). If enabled, the following process is effected. When robot 101 is
enabled, a command position of robot 101 is calculated from a present
value of the clock of robot 101 (step 162). The command position is
outputted to servo amplifier section B-7 of robot 101 (step 163).
Subsequently, in a block g-1 in FIG. 9B, the process for work suction-ON
is carried out. In the block g-1, it is checked whether or not the clock
of robot 101 is identical to the clock value of work suction-ON (step
164). If identical, it is checked whether the upstream unit, that is, the
associated unit from which work is received, is enabled (step 165) and
whether the work transfer mode is "2" or not (step 166). In addition, if
work is held by the upstream unit, the work suction signal of robot 101 is
turned on (step 168), and at the same time, work existence signal of robot
is turned on (step 169).
Subsequently in the processing section g-3 of FIG. 9B, the process for
turning off work suction of robot 101 is carried out. In this section, it
is first checked whether the clock of robot 101 is identical to the clock
value of work section-OFF of robot 101 (step 174). If identical, it is
checked whether the downstream unit, which is the associated unit to which
work is handed, is enabled or not (step 175) and whether work transfer
mode of robot is "0" or not (step 176). On the other hand, if work is not
present, the suction signal of robot 101 is turned off (step 178), and at
the same time, work existence signal of robot 101 is turned off (step
179). The operational routine of robot 101 controlling section has been
described. The same routine is similarly applied to robot 102 and 103.
The foregoing is the difference between previously described embodiment and
the present embodiment. According to the process described above, it is
possible to operate the respective robots in synchronism with each other.
Further, it is possible to exactly judge robots to be enabled in
accordance with the existence/absence of work on each robot. In addition,
in the case where work is transferred between the two robots, since the
two robots operate in synchronism, the relative speed may be decreased at
zero to thereby smoothly perform the transfer job. The operational loci of
robots in the industrial robot system of this embodiment are shown in FIG.
8B.
Although the present invention has been described on the basis of the
embodiments, it is to be understood that various modifications can be made
to the specific forms 1 and/or the invention may be embodied in other
forms within the scope of the appended claims.
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